What is a defensible regulatory risk assessment?

An effective and defensible risk assessment of dental amalgam requires a detailed quantitative analysis of the exposure to mercury vapor in the general population. However, the FDA only alludes to average or typical exposure levels, citing dated (predating 1993) reviews which they themselves only cite other yet older reviews.

A typical, defensible regulatory risk assessment for chemical exposure would quantify that exposure in across the entire general population, and particularly in the ‘reasonably maximally exposed’ portion of the US population, not just some undefined average or typical person. To achieve this, data on the range (minimum to maximum) of that chemical exposureacross all members of the general population is required. Unfortunately, with respect to mercury vapor exposure from dental amalgam, the FDA never quantifies exposure in those members of the US population who are maximally exposed – those with up to twenty-five amalgam-filled teeth.

The FDA only considers those with up to ten amalgam fillings.

Further, a defensible risk assessment does not exclude any segment of the US population.

Unfortunately, the FDA never even attempted to quantify the mercury exposure in children under six years of age, despite it being known that children as young as 3 years of age do receive amalgam fillings and, as a result, are exposed to mercury vapor from this source. The significance of this oversight is compounded by the fact that risk assessment guidance for neurotoxic agents such as mercury vapor (see USEPA 1998) specifically stipulates the importance of considering infants and young children in whom neurotoxicity will be pronounced due to the susceptibility of the growing and developing brain to the effects of neurotoxins.

To demonstrate that such an exposure assessment is possible and feasible, the Canadian government, in its risk assessment of dental amalgam (Health Canada, 1995) was open and transparent about the prevalence of mercury fillings in the Canadian population, with adults having up to 25 filled teeth and children as young as 3 years of age having filled teeth.Health Canada was also explicit in the methods used to estimate exposures, to the point of providing estimates of mercury vapor exposure per filled tooth, for each of five separate age groups (toddlers, children, teens, adults and seniors).

Health Canada neither omitted to determine exposure in persons with more than 10 fillings, nor omitted to consider children less than 6 years of age.

Both such considerations were omitted by the FDA in their final rule.

[readon url=”index.php?option=com_content&view=article&id=202&Itemid=237″]What reference levels should exposures be compared to?[/readon]

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